Sterilizing method and sterilizer

ABSTRACT

A sterilizing method for sterilizing a sterilization object housed in a chamber 11 includes a first vapor injection step S502 for injecting vapor produced from a first aqueous solution of hydrogen peroxide to an inside of the chamber 11, an ozone injection step S505 for injecting ozone gas to the inside of the chamber 11 after the first vapor injection step S502, and a second vapor injection step S507 for injecting vapor produced from a second aqueous solution of hydrogen peroxide to the inside of the chamber 11 after the ozone injection step S505. A total amount of the hydrogen peroxide included in the second aqueous solution is smaller than or equal to a total amount of the hydrogen peroxide included in the first aqueous solution.

TECHNICAL FIELD

The present disclosure relates to a sterilizing method and a sterilizer.

BACKGROUND ART

Reusable medical instruments used for surgical operations and medicalcares in hospitals are subjected to treatment of sterilization aftersufficient cleaning in order to remove adhesive matter such as blood andprotein.

A sterilizing method is known that uses hydrogen peroxide as mainsterilization gas and further uses additional gas for executing suchsterilization treatment in order to improve the sterilizationefficiency. Patent Literature 1 discloses sterilizing method andapparatus that execute a series of steps of reducing a pressure in achamber housing an object to be sterilized, injecting vapor of anaqueous solution of hydrogen peroxide for sterilization to keep thestate, and further injecting ozone gas for sterilization to keep thestate.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent No. 5480975

SUMMARY OF THE INVENTION

The sterilizing method disclosed in Patent Literature 1 only keeps thesterilizing state after the injection of the ozone gas. The inventorshave confirmed through reproducibility tests that the sterilizationeffect is not particularly improved by the ozone gas. The sterilizingmethod and apparatus using plural kinds of sterilization gas thus stillneed to be improved in order to enhance the sterilization efficiency.Simply increasing the amount of the sterilization gas to be used only inview of the improvement in the sterilization efficiency, however, leadsto an increase in operating costs of the sterilizing apparatus, or hasan unfavorable effect on the environment.

An object of the present disclosure is to provide a sterilizing methodand a sterilizer capable of improving a sterilization efficiency in theentire sterilizing treatment while contributing to a decrease in theamount of hydrogen peroxide to be used.

Solution to Problem

A first aspect of the present disclosure provides a sterilizing methodfor sterilizing a sterilization object housed in a chamber, the methodincluding a first vapor injection step of injecting vapor produced froma first aqueous solution of hydrogen peroxide to an inside of thechamber, an ozone injection step of injecting ozone gas to the inside ofthe chamber after the first vapor injection step, and a second vaporinjection step of injecting vapor produced from a second aqueoussolution of hydrogen peroxide to the inside of the chamber after theozone injection step, wherein a total amount of the hydrogen peroxideincluded in the second aqueous solution is smaller than or equal to atotal amount of the hydrogen peroxide included in the first aqueoussolution.

A second aspect of the present disclosure provides a sterilizerincluding a chamber configured to house a sterilization object, anevaporator configured to communicate with the chamber and evaporate afirst aqueous solution of hydrogen peroxide or a second aqueous solutionof hydrogen peroxide so as to be filled therewith, an ozone generatorconfigured to communicate with the chamber and produce ozone gas, and acontroller configured to control an operation of injecting, to an insideof the chamber, vapor produced by the evaporator or the ozone gasproduced by the ozone generator, wherein a total amount of the hydrogenperoxide included in the second aqueous solution is smaller than orequal to a total amount of the hydrogen peroxide included in the firstaqueous solution, and the controller injects the ozone gas to the insideof the chamber after injecting the vapor produced from the first aqueoussolution, and injects the vapor produced from the second aqueoussolution to the inside of the chamber after injecting the ozone gas soas to sterilize the sterilization object.

Advantageous Effects

The present disclosure can provide a sterilizing method and a sterilizercapable of improving a sterilization efficiency in the entiresterilizing treatment while contributing to a decrease in the amount ofhydrogen peroxide to be used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a sterilizeraccording to a first embodiment of the present disclosure.

FIG. 2 is a flowchart showing a process of sterilizing method accordingto the first embodiment.

FIG. 3 is a graph showing a change in pressure inside a chamberaccording to the first embodiment.

FIG. 4 is a table showing plural processing modes executed by thesterilizer according to the first embodiment.

FIG. 5 is a flowchart showing a process of sterilization steps accordingto the first embodiment.

FIG. 6 is a flowchart showing a procedure of a sterilizing methodaccording to a second embodiment.

FIG. 7 is a table showing various kinds of conditions used for asterilization treatment test according to the second embodiment.

FIG. 8 is a table showing results of the sterilization treatment testexecuted under the conditions shown in FIG. 7 .

FIG. 9 is a graph showing a change in pressure inside the chamber in acase of Comparative Example 1.

FIG. 10 is a graph showing a change in pressure inside the chamber in acase of Comparative Example 2.

FIG. 11 is a graph showing a change in pressure inside the chamber in acase of Example.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail belowwith reference to the drawings. The following dimensions, materials, andspecific numerical values described in the respective embodiments areindicated for illustration purposes, and the present disclosure is notintended to be limited thereto unless otherwise specified. The elementshaving substantially the same functions and structures illustrated beloware designated by the same reference numerals, and overlappingexplanations are not made below. The elements described below but notrelated directly to the present disclosure are not shown in thedrawings.

First Embodiment

FIG. 1 is a schematic diagram showing a configuration of a sterilizer100 according to a first embodiment. The sterilizer 100 sterilizes anobject to be sterilize by use of sterilization gas. Materials mainlyincluded in the sterilization gas used in the present embodiment arehydrogen peroxide (H₂O₂) and ozone (O₃).

The object to be sterilized is herein presumed to be a medicalinstrument used in a hospital for surgical operations and medical caresand brought into contact with a blood circulatory system or aseptictissues. Examples of medical instruments include a heat-resistant steelproduct such as a pair of forceps, a surgical tweezer, and surgicalscissors, and a non-heat resistant resin product such as a hardendoscope made of stainless steel used for laparoscopic surgery, a softendoscope used for bronchial or urinary surgery, and a power supplycable as an attachment for these endoscopes. The object to be sterilizedis herein presumed to be housed in a chamber 11 of the sterilizer 100 ina state of being preliminarily wrapped with a wrapping material in orderto prevent re-contamination after the sterilization. The wrappingmaterial is, for example, nonwoven fabric of fine mesh, which passes thesterilization gas but barely passes bacteria therethrough. The nonwovenfabric may mainly include resin material such as polyethylene. Thewrapping material of this type is sometimes referred to also as asterilization bag or sterilization wrap.

The sterilizer 100 includes a chamber unit 10, a hydrogen peroxidesupply unit 20, an ozone supply unit 30, an exhaustion unit 40, an airintroduction unit 50, and a control unit 60.

The chamber unit 10 includes the chamber 11 for housing the object to besterilized, and peripheral components. The chamber unit 10 includes thechamber 11 having a door 12, a first heater 13, and a first manometer14.

The chamber 11 is a holder for housing and placing the object to besterilized therein. The chamber 11 is referred to also as asterilization container. The chamber 11 is made of stainless steel or analuminum alloy, and has a structure resistant to a vacuum anddecompression. The present embodiment is illustrated below with a casein which a capacity of the chamber 11 is 100 liters (L), for example.The door 12 is arranged on the chamber 11 in an openable manner. Thechamber 11 is tightly sealed to prevent vacuum leakage or leakage of thesterilization gas when the door 12 is closed so that the inside of thechamber 11 is decompressed.

The first heater 13 is installed at a circumference of the chamber 11together with a thermal material to keep the internal temperature of thechamber 11 constant during the sterilization treatment. The temperatureof the chamber 11 is measured by a thermometer (not illustrated)arranged at the chamber 11.

The first manometer 14 is a vacuum gauge arranged at the chamber 11 tomeasure the pressure inside the chamber 11.

The hydrogen peroxide supply unit 20 supplies vapor of hydrogen peroxideto the chamber 11 during the sterilization treatment. The hydrogenperoxide supply unit 20 according to the present embodiment canindependently supply the vapor separately produced from two aqueoussolutions of hydrogen peroxide. One of the aqueous solutions of hydrogenperoxide is referred to below as a “first aqueous solution”, and theother aqueous solution of hydrogen peroxide is referred to below as a“second aqueous solution”. A concentration of the hydrogen peroxidecontained in the first aqueous solution or the second aqueous solution,or a total amount of the hydrogen peroxide contained in the firstaqueous solution or the second aqueous solution is determined accordingto the presence or absence of a duct part in the object to be sterilizedor the material used for the object to be sterilized, as describedbelow. The hydrogen peroxide supply unit 20 includes a bottle 21, anextraction pipe 22, a tube pump 23, a storage part 24, an evaporator 26,and a second heater 29.

The bottle 21 houses the aqueous solution of the hydrogen peroxide. Thebottle 21, when exposable, is referred to also as a cartridge. Thepresent embodiment uses the two aqueous solutions of the hydrogenperoxide, and uses a first bottle 21 a for housing the first aqueoussolution and a second bottle 21 b for housing the second aqueoussolution.

The extraction pipe 22 extracts the aqueous solutions of the hydrogenperoxide from the respective bottles 21, and supplies the extractedaqueous solutions to the storage part 24. The present embodiment uses afirst extraction pipe 22 a that extracts the first aqueous solution fromthe first bottle 21 a, and a second extraction pipe 22 b that extractsthe second aqueous solution from the second bottle 21 b.

The tube pump 23 is arranged in the middle of the respective extractionpipes 22 to suck an appropriate amount of the aqueous solutions of thehydrogen peroxide every time out of the respective bottles 21. Thepresent embodiment uses a first tube pump 23 a arranged in the middle ofthe first extraction pipe 22 a, and a second tube pump 23 b arranged inthe middle of the second extraction pipe 22 b. The respective extractionpipes 22 may be provided with an optical liquid level sensor (notillustrated), for example. The respective tube pumps 23 suck up theaqueous solutions of the hydrogen peroxide until the liquid level sensorresponds, and temporarily stop upon the response of the liquid levelsensor and then rotate with a predetermined number of times, so as tosupply the predetermined amount of the respective aqueous solutions tothe storage part 24.

The storage part 24 is connected to the respective extraction pipes 22to temporarily store the predetermined amount of the respective aqueoussolutions of the hydrogen peroxide sucked out of the bottles 21 beforethe supply to the evaporator 26. The storage part 24 used may be asemi-transparent fluororesin tube through which the amount of thesolution stored inside can be visually confirmed. Since the respectivetube pumps 23 can supply the constant amount of the solution stably whendriven under an atmospheric pressure, the storage part 24 may besupplied with the air via a first filter 25 so as to be under theatmospheric pressure. The first filter 25 is a high-efficiencyparticulate air (HEPA) filter, for example.

The evaporator 26 communicates with the storage part 24 via a firstsupply pipe 27, and evaporates the aqueous solution of the hydrogenperoxide introduced through the storage part 24. The evaporator 26 is,for example, made of stainless steel so as to have resistance tocorrosion caused by the hydrogen peroxide, and has a structure resistantto a vacuum and decompression since the evaporator 26 is decompressedsimultaneously with the chamber 11.

The first supply pipe 27 is provided with a first electromagnetic valve70. When the first electromagnetic valve 70 is open, the aqueoussolution of the hydrogen peroxide stored in the storage part 24 issucked and introduced toward the decompressed evaporator 26. Since thestorage part 24 is under the atmospheric pressure after being suppliedwith the air via the first filter 25, the air is also sucked togetherwith the aqueous solution of the hydrogen peroxide. The aqueous solutionof the hydrogen peroxide remaining in the storage part 24 and the firstsupply pipe 27 is also sucked and introduced toward the evaporator 26,so that the constant amount of the vapor of the hydrogen peroxide isstably supplied to the inside of the chamber 11.

The evaporator 26 communicates with the chamber 11 via a plurality ofinjection pipes 28. The present embodiment uses a first injection pipe28 a and a second injection pipe 28 b arranged on a ceiling at twopositions in the diagonal line. The first injection pipe 28 a isprovided with a second electromagnetic valve 71, and the secondinjection pipe 28 b is provided with a third electromagnetic valve 72.When the aqueous solution of the hydrogen peroxide is evaporated in theevaporator 26 to increase the pressure inside the evaporator 26, thesecond electromagnetic valve 71 or the third electromagnetic valve 72 isopened for a predetermined period of time, so that the vapor of theaqueous solution of the hydrogen peroxide is injected to the inside ofthe chamber 11. The arrangement of the plural injection pipes 28 asdescribed above can further enhance the uniform diffusion of the vaporinside the chamber 11. The evaporator 26 may be provided with a pressuresensor 39 for determining whether the pressure inside the evaporator 26is increased to a level within a predetermined range after the injectionof the vapor so as to determine whether the predetermined amount of thevapor is supplied from the storage part 24.

The second heater 29 is arranged at a circumference of the evaporator 26to keep the internal temperature of the evaporator 26 constant. Theinside of the evaporator 26 is constantly kept at a predeterminedtemperature in a range of 65° C. to 120° C., for example.

The ozone supply unit 30 supplies the ozone gas to the chamber 11 duringthe sterilization treatment. The ozone gas used in the presentembodiment is produced inside the ozone supply unit 30. The ozone supplyunit 30 includes an oxygen generation device 31, an ozone generator 32,an ozone densitometer 33, a buffer tank 34, and a second manometer 35.

The oxygen generation device 31 produces oxygen (O₂) serving as rawmaterial of ozone. The oxygen generation device 31 can adopt a pressureswing adsorption (PSA) mode that causes nitrogen in the air to beadsorbed to an adsorbent such as zeolite to produce oxygen with a highconcentration. In particular, the oxygen generation device 31 may be aPSA device having a discharge pressure in a range of about 0.03 to 0.08MPa as a gauge pressure, and a flowing amount in a range of about 1 to 4L/min A pipe connecting the oxygen generation device 31 and the ozonegenerator 32 is provided with a fourth electromagnetic valve 73.Controlling the open and closed states of the fourth electromagneticvalve 73 as appropriate can regulate the supply amount of the oxygen tothe ozone generator 32.

The ozone generator 32 produces the ozone gas from the oxygen producedby the oxygen generation device 31. The ozone generator 32 can adopt asilent discharge mode that applies a high voltage with a high frequencyto the oxygen to be discharged and decomposed so as to produce theozone. The present embodiment is illustrated with a case in which theozone supply unit 30 includes two ozone generators 32. A productionability of the ozone generators 32 is given by 2 g/hr×two ozonegenerators=4 g/hr, for example. The ozone generators 32 in this caseoperate for 1.5 minutes while receiving 1 L/min of the oxygen, so as toproduce the ozone with the amount given by 4 g×1.5 minutes/60minutes=0.1 g. The ozone generators 32 communicate with the buffer tank34 via a second supply pipe 36.

The ozone densitometer 33 measures a concentration of the ozone gasproduced by the ozone generators 32 in the second supply pipe 36. Forexample, a case is presumed in which a measurement value obtained by theozone densitometer 33 is 70 g/m³ when the ozone gas is allowed to flowthrough the second supply pipe 36 for 1.5 minutes with the flowingamount of 1 L/min. The amount of the ozone produced in this casecorresponds to the amount given by 1 L/min×1.5 minutes×70 g/1000 L=0.105g. In addition, a case is presumed in which 0.105 g of the ozone gas isinjected to the inside of the chamber 11 with the capacity of 100 L, andthe air is further introduced thereto so as to be under the atmosphericpressure. The concentration of the ozone in the chamber 11 in this casecorresponds to a volume concentration given by 0.105 g/48 g×22.4 L/100L×1,000,000=490 ppm, where 48 g is a molecular amount of the ozone, and22.4 L is the amount of reference gas.

The second supply pipe 36 is provided with a fifth electromagnetic valve74 between the ozone densitometer 33 and the buffer tank 34. The secondsupply pipe 36 between the ozone densitometer 33 and the fifthelectromagnetic valve 74 may communicate with the exhaustion unit 40 viaa piping system X including a sixth electromagnetic valve 75. When thefifth electromagnetic valve 74 is closed and the sixth electromagneticvalve 75 is open, the ozone gas flowing from the respective ozonegenerators 32 is supplied toward the exhaustion unit 40.

The buffer tank 34 temporarily stores the ozone gas produced by therespective ozone generators 32 before the supply to the evaporator 26.The buffer tank 34 is, for example, made of stainless steel so as tohave resistance to corrosion caused by the hydrogen peroxide, and has astructure resistant to decompression. The present embodiment isillustrated below with a case in which a capacity of the buffer tank 34is two liters (L). The buffer tank 34 communicates with the evaporator26 via a third supply pipe 37. The third supply pipe 37 is provided witha seventh electromagnetic valve 76. When the ozone gas is injected tothe buffer tank 34 while the seventh electromagnetic valve 76 is closed,the pressure inside the buffer tank 34 is transiently increased.

The second manometer 35 is a vacuum gauge arranged at the buffer tank 34to measure the pressure inside the buffer tank 34. A controller 61monitors the pressure inside the buffer tank 34 by use of the secondmanometer 35, so as to confirm whether the ozone injected is increasedto a predetermined pressure in the buffer tank 34, or confirm whetherleakage or stoppage of the ozone is caused in the second supply pipe 36or the like.

According to the present embodiment, the ozone gas supplied from thebuffer tank 34 is not directly but indirectly injected to the chamber 11via the evaporator 26. An introduction port of the sterilization gastoward the chamber 11 is shared with the hydrogen peroxide and the ozonegas.

As another embodiment, the ozone gas may be directly injected to thechamber 11 from the buffer tank 34 without bypassing the evaporator 26.The direct injection of the ozone gas to the chamber 11 withoutbypassing the evaporator 26 has the advantage of increasing the speed ofdiffusion of the ozone gas inside the chamber 11. This case also has theadvantage of increasing the ozone concentration in the chamber 11 whenthe second electromagnetic valve 71 and the third electric valve 72arranged between the evaporator 26 and the chamber 11 are closed.

The exhaustion unit 40 vents the atmosphere inside the chamber 11 so asto decompress the inside of the chamber 11 or discharge the gas presentinside the chamber 11 to the outside. In particular, the exhaustion unit40 removes excessive gas from the chamber 11 or the object to besterilized itself to decompress the inside of the chamber 11 to a mediumvacuum level of 100 Pa or below, for example, before the sterilizationtreatment in order to improve the sterilization effect during thesterilization treatment. The exhaustion unit 40 also eliminates thesterilization gas remaining in the chamber 11 or the object to besterilized after the sterilization treatment. The exhaustion unit 40includes a vacuum pump 41, a catalyst tank, and a heater.

The vacuum pump 41 used can be a dry pump such as a scroll pump formedium vacuum, or a hydraulic rotating pump such as a rotary pump. Thevacuum pump 41 in the present embodiment is a hydraulic rotating pump.The vacuum pump 41 and the chamber 11 communicate with each other via anexhaustion pipe 38. The exhaustion pipe 38 is provided with an eighthelectromagnetic valve 77. When the pressure inside the chamber 11reaches a predetermined value during the compression, for example, thecontroller 61 closes the eighth electromagnetic valve 77 to stop theoperation of the vacuum pump 41.

The catalyst tank is made of stainless steel, for example, and includesa catalyst such as a pellet type and a honeycomb type. The catalystmainly includes manganese dioxide, for example, and decomposes thehydrogen peroxide and the ozone. The catalyst tank in the presentembodiment is arranged at two positions on the upstream side and thedownstream side of the vacuum pump 41 in view of decomposing gas havinga risk of corroding the vacuum pump, and also keeping the exhaustionspeed as appropriate. A first catalyst tank 42 is a catalyst tankarranged on the upstream side of the vacuum pump 41. A second catalysttank 43 is a catalyst tank arranged on the downstream side of the vacuumpump 41.

As described above, the ozone supply unit 30 can supply the ozone gas tothe exhaustion unit 40 via the piping system X such that the ozonegenerators 32, the fifth electromagnetic valve 74, and the sixthelectromagnetic valve 75 are controlled as appropriate.

The heater keeps the respective catalyst tanks at a temperature in arange of 60° C. to 90° C., for example. A third heater 44 keeps thetemperature of the first catalyst tank 42. A fourth heater 45 keeps thetemperature of the second catalyst tank 43.

The air introduction unit 50 introduces the air into the inside of thechamber 11. The air introduction unit 50 includes a second filter 51 anda plurality of introduction ports.

The second filter 51 prevents dust in the air from entering the insideof the chamber 11 upon the introduction of the air. The second filter 51used may be a HEPA filter which is a nonwoven filter of fine mesh, forexample.

The respective introduction ports introduce the air through the secondfilter 51 to the inside of the chamber 11. The introduction ports arepreferably arranged at different positions from each other in thechamber 11 in order to equalize the gas concentration inside the chamber11 simultaneously with the introduction of the air. The presentembodiment uses two introduction ports, a first introduction port 52 anda second introduction port 53, for example, arranged on the ceiling attwo positions in the diagonal line. The first introduction port 52 isprovided with a ninth electromagnetic valve 78. The second introductionport 53 is provided with a tenth electromagnetic valve 79. Thecontroller 61 independently controls the open and closed states of theninth electromagnetic valve 78 and the tenth electromagnetic valve 79,so as to introduce the air into the inside of the chamber 11 from thedifferent positions at an appropriate timing.

The introduction ports are not limited to those directly arranged at thechamber 11. As another embodiment, the introduction ports may beconnected to the chamber 11 via the evaporator 26, or the introductionports may be connected to the chamber 11 via the buffer tank 34. Theintroduction ports may also be connected to the chamber 11 via both theevaporator 26 and the buffer tank 34, for example.

The control unit 60 controls the driving operations of power systemelements in the respective units included in the sterilizer 100 inaccordance with various kinds of operating commands. The control unit 60includes the controller 61 and a touch panel 62. The controller 61 iselectrically connected to the respective power system elements andmeasurement system elements, for example. The controller 61 controls theoperations of the respective power system elements in accordance with acommand input via the touch panel 62, a sequence of control operationspreliminarily stored, or a detection signal acquired from various typesof sensors. The touch panel 62 is electrically connected to thecontroller 61, and is used by the operator to input the information orcommand and to visually recognize the information provided from thesterilizer side.

Next, a process of a sterilizing method according to the presentembodiment by use of the sterilizer 100 is described below.

FIG. 2 is a flowchart showing the process of the sterilizing methodaccording to the present embodiment. FIG. 3 is a graph showing a changein pressure inside the chamber 11 with a lapse of time through theprocess of the sterilizing method according to the present embodiment.

The sterilizing method according to the present embodiment includes atreatment mode selection step S100, a preliminary decompression stepS200, an ozone adsorption step S300, a sterilization decompression stepS400, a sterilization step S500, and an aeration step S700.

Before starting the treatment mode selection step S100, the operatorsuch as a nurse in a hospital places the object to be sterilized wrappedwith a wrapping material in the chamber 11, and closes the door 12 tomake the inside of the chamber 11 airtight. At this point, the power ofthe sterilizer 100 is presumed to be already turned on so as to completea warming-up.

In the sterilization treatment in the present embodiment, the operatorcan choose a treatment mode depending on the type of the object to besterilized. The type of the object to be sterilized is classifiedaccording to the shape and the material of the object to be sterilized,for example. In particular, the shape of the object to be sterilized maybe classified in accordance with the presence or absence of a duct part.The treatment mode selection step S100 is a step of inputting thetreatment mode chosen by the operator to the sterilizer 100.

FIG. 4 is a table showing the respective treatment modes executable bythe sterilizer 100. The treatment modes may include the following threemodes, for example. A short mode is applied to a case in which theobject to be sterilized is a medical instrument having no duct part. Themedical instrument of this type is a steel product such as a pair offorceps, for example, and is mainly subjected to surface sterilization.A normal mode is applied to a case in which the object to be sterilizedis a medical instrument made of resin having a duct part. A long mode isapplied to a case in which the object to be sterilized is a medicalinstrument made of stainless steel having a duct part. The medicalinstrument of this type is a hard endoscope having a thin tube with aninner diameter of about 1 mm, for example.

The treatment modes differ from each other in the treatment time, theinjected amount of the aqueous solution of the hydrogen peroxide, or thenumber of exposure times in the following steps. The column of theinjected amount of the aqueous solution of the hydrogen peroxide in thetable shown in FIG. 4 indicates a range of possible values per pulsecorresponding to one operation of the sterilization step S500 describedbelow. In particular, the upper row in the column indicates the algebraregarding the injected amount of the first aqueous solution, and thelower row indicates the algebra regarding the injected amount of thesecond aqueous solution.

The preliminary decompression step S200 is a step executed preliminaryto the following ozone adsorption step S300 to decompress the inside ofthe chamber 11 with respect to the atmospheric pressure. FIG. 3indicates a period in which the preliminary decompression step S200 isexecuted by H11. The preliminary decompression step S200 decompressesthe inside of the chamber 11 to a level of 100 Pa, for example.

The ozone adsorption step S300 is a step of injecting the ozone gas tothe inside of the chamber 11 under the decompressed state obtained bythe preliminary decompression step S200 to cause the ozone gas to beadsorbed to the wrapping material wrapping the object to be sterilized.The present embodiment executes an ozone injection step S505 separatelyfrom the ozone adsorption step S300. If the ozone adsorption step S300would not be executed, the ozone gas injected to the inside of thechamber 11 in the ozone injection step S505 would be adsorbed to thewrapping material wrapping the object to be sterilized. The ozone as anadsorbent may prevent the ozone gas sequentially supplied from reachingthe object to be sterilized. The present embodiment thus causes theozone gas to be adsorbed to the wrapping material in the ozoneadsorption step S300 before executing the ozone injection step S505 tolead the wrapping material to a saturated state or a state approximateto the saturated state. Preliminarily leading the wrapping material tothe saturated state or the state approximate to the saturated state canavoid or decrease the adsorption of the ozone gas to the wrappingmaterial when injecting the ozone gas to the inside of the chamber 11 inthe ozone injection step S505, so as to allow the ozone gas to easilyreach the object to be sterilized accordingly. Some of the ozone gasinjected in the ozone adsorption step S300 reaches the object to besterilized to contribute to the sterilization, in addition to the ozonegas being adsorbed to the wrapping material.

The execution of the following ozone injection step S505 might beeliminated when the concentration of the ozone gas in the gas suppliedto the inside of the chamber 11 is increased in the ozone adsorptionstep S300. The execution of the ozone adsorption step S300 might beeliminated instead when the concentration of the ozone gas in the gassupplied to the inside of the chamber 11 is increased in the ozoneinjection step S505. However, the increase in the concentration of theozone gas as described above might have an unintended influence thatwould cause deformation of the object to be sterilized, for example,depending on the material used for the object to be sterilized. Theseries of steps in the sterilizing method according to the presentembodiment thus includes the plural steps for injecting the ozone gas tothe inside of the chamber 11 several times, so as to avoid or decreasethe influence of the ozone gas on the shape or composition of the objectto be sterilized more reliably. In view of the decrease in the influenceof the ozone gas as described above, the gas to be supplied to theinside of the chamber 11 in the ozone adsorption step S300 is defined tocontain the ozone gas with the concentration of about 1%. When the ozonegas is presumed to be produced in the ozone supply unit 30 as describedin the present embodiment, the gas to be supplied to the inside of thechamber 11 contains 99% of oxygen excluding the ozone gas. If theconcentration of the ozone gas is defined to be higher, the constituentmembers such as the ozone generators 32 that produce the ozone gas mayneed to have higher performance. Setting the concentration of the ozonegas to about 1% has the advantage of facilitating the ozone generationby the ozone generators 32. Setting the concentration of the ozone gasto about 1% also has the advantage of avoiding an unintended influenceon the object to be sterilized, since the concentration of the ozone gasafter the injection to the inside of the chamber 11 can be decreased to500 ppm or lower.

FIG. 3 indicates the timing of starting the ozone adsorption step S300by T11. The internal state of the chamber 11 may be kept during a periodH12 after the ozone gas is injected to the inside of the chamber 11 inthe ozone adsorption step S300, as shown in FIG. 3 . For example, whenthe treatment mode is the short mode, the concentration of the ozone gasin the ozone adsorption step S300 may be about 400 ppm, while thekeeping time corresponding to the period H12 may be three minutes. Anexposure condition for the ozone gas in this case is approximately givenby 400 (ppm)×3 (minutes)=1200 (ppm/min). The control by the controller61 upon the injection of the ozone gas is the same as the control in theozone injection step S505 described below. In addition, a preparationstep similar to an ozone preparation step S504 described below may beexecuted before the ozone adsorption step S300.

As illustrated above, the gas supplied to the inside of the chamber 11in the ozone adsorption step S300 contains a great amount of the oxygen,as compared with the ozone gas. The present embodiment then injects thevapor of the first aqueous solution of the hydrogen peroxide to theinside of the chamber 11 in a first vapor injection step S502. Thehydrogen peroxide cannot easily reach the surface of the object to besterilized when the vapor of the first aqueous solution is injected tothe inside of the chamber 11 in the first vapor injection step S502 if alarge amount of the oxygen remains inside the chamber 11. Thesterilization decompression step S400 is a step executed in view of sucha problem to remove the oxygen remaining inside the chamber 11 beforethe first vapor injection step S502. Decompressing the inside of thechamber 11 in the sterilization decompression step S400 can increase theamount of the hydrogen peroxide reaching the object to be sterilized.

In the sterilization decompression step S400, the controller 61 opensthe eighth electromagnetic valve 77 after driving the vacuum pump 41 soas to decompress the inside of the chamber 11 during a period H13 shownin FIG. 3 . The controller 61 further opens the second electromagneticvalue 71, the third electromagnetic value 72, and the seventhelectromagnetic value 76, so as to decompress the inside of each of theevaporator 26 and the buffer tank 34, in addition to the chamber 11. Thetreatment time indicated in the table shown in FIG. 4 is measured fromthe point of starting the decompression in this case.

A target pressure in the sterilization decompression step S400 is set toa pressure sufficient to remove the oxygen and lead the vapor of thefirst aqueous solution of the hydrogen peroxide to reach the object tobe sterilized reliably in the following first vapor injection step S502.For example, the target pressure in this case is set to 50 Pa or lower,and particularly preferably set in a range of 25 to 35 Pa.

The controller 61, when the pressure reaches the target pressure, closesthe second electromagnetic valve 71, the third electromagnetic valve 72,the seventh electromagnetic valve 76, and the eighth electromagneticvalve 77 to stop the vacuum pump 41. The controller 61 then leads theprocess to proceed to the sterilization step S500 after thesterilization decompression step S400. The internal state of the chamber11 may be kept during a period H14 after the sterilization decompressionstep S400, as shown in FIG. 3 .

When the treatment mode is the long mode, the object to be sterilized isa thin tube made of stainless steel, for example. Upon the choice of thelong mode, the temperature of the object to be sterilized may bepreliminarily increased and kept for a predetermined period of time suchas about two minutes while keeping the state of the pressure reached, soas to reduce an influence of water condensation inside the duct part asmuch as possible.

FIG. 5 is a flowchart showing a process of the sterilization step S500.The sterilization step S500 is a step mainly contributing to thesterilization of the object to be sterilized. The sterilization stepS500 includes a first vapor preparation step S501, the first vaporinjection step S502, and a first state-keeping step S503.

The first vapor preparation step S501 is a step of producing the vaporof the first aqueous solution to be injected in the following firstvapor injection step S502. The controller 61 first rotates the firsttube pump 23 a to suck the first aqueous solution from the first bottle21 a, and then injects an equally-divided amount of the defined amountof the first aqueous solution to the storage part 24. The defined amountis a total injected amount per pulse, and differs from the respectivetreatment modes as shown in FIG. 3 . For example, when the treatmentmode is the short mode, the concentration of the hydrogen peroxidecontained in the first aqueous solution is set to a predeterminedconcentration (x1) in a range of 30% to 60%, and the defined amount is apredetermined amount (y1) in a range of 1 to 4 ml. When the definedamount is divided by two and is then injected, for example, theequally-divided amount of the defined amount is half of y1, which is apredetermined amount (y1/2) in a range of 0.5 to 2 ml. The controller 61then opens the first electromagnetic valve 70 for a predetermined periodof time such as five seconds. Since the inside of the evaporator 26 hasbeen already decompressed, the first aqueous solution is immediatelysucked up to the evaporator 26. The air then enters the storage part 24,which communicates with the atmosphere, via the first filter 25 so thatthe first aqueous solution remaining in the storage part 24 or the firstsupply pipe 27 is also sent to the evaporator 26. The controller 61 thencloses the first electromagnetic valve 70 to evaporate the first aqueoussolution in the evaporator 26 for a predetermined period of time such asfive seconds. The evaporator 26 is constantly kept at a predeterminedtemperature in a range of 65° C. to 120° C., for example. When aregulated amount of the first aqueous solution is injected so as to besubstantially completely evaporated inside the evaporator 26 with apredetermined value within a capacity in a range of 0.5 to 2 L under apressure of 50 Pa, for example, the pressure is presumed to be increasedto a level of about a saturated vapor pressure. The controller 61 thenleads the process to proceed to the first vapor injection step S502after the first vapor preparation step S501.

The first vapor injection step S502 is a step of injecting the vapor ofthe first aqueous solution produced by the evaporator 26 to the insideof the chamber 11. FIG. 3 indicates the timing of starting the firstvapor injection step S502 by T12. The controller 61 first opens thesecond electromagnetic valve 71 and the third electromagnetic valve 72for a predetermined period of time such as ten seconds. The vapor of thefirst aqueous solution is then strongly injected to the inside of thechamber 11 due to the difference in the pressure. When the object to besterilized particularly has a duct part, the vapor penetrates the insideof the duct part more easily as the difference in the pressure ishigher. In addition, the vapor is easily equalized inside the chamber 11as described above. The controller 61 then closes the secondelectromagnetic valve 71 and the third electromagnetic valve 72. Thecontroller 61 repeats the injection of the vapor of the first aqueoussolution in the same process in accordance with the respective treatmentmodes. For example, when the treatment mode is the short mode, the vaporof the first aqueous solution is to be injected to the evaporator 26 perpulse with an amount corresponding to the predetermined concentration(x1) in the range of 30% to 60% to be multiplied by the predeterminedamount (y1) in the range of 1 to 4 ml. If a large amount of the firstaqueous solution is injected at once, the inside of the evaporator 26reaches the saturated vapor pressure, which may impede the sufficientevaporation to cause the first aqueous solution to remain in theevaporator 26. In view of this, the controller 61 may divide the amountof the first aqueous solution by two so as to evaporate and sequentiallyinject the second aqueous solution half-and-half to the chamber 11. Thecontroller 61 may divide the amount of the first aqueous solution intomore than two so as to sequentially inject the vapor of the firstaqueous solution to the chamber 11. The controller 61 then leads theprocess to proceed to the first state-keeping step S503 after the firstvapor injection step S502.

The first state-keeping step S503 is a step of keeping the vapor of thefirst aqueous solution in the chamber 11 for a predetermined period oftime to sterilize the object to be sterilized. FIG. 3 indicates thepredetermined keeping time by H15. The keeping time in the respectivetreatment modes in this case differs from each other. The keeping timein the short mode is three minutes, for example. The keeping time in thenormal mode is four minutes, for example. The keeping time in the longmode is six minutes. The keeping time gradually increases in the orderof the short mode, the normal mode, and the long mode.

The sterilization step S500 includes the ozone preparation step S504 andthe ozone injection step S505.

The ozone preparation step S504 is a step of producing the ozone gas tobe injected in the following ozone injection step S505. The ozonepreparation step S504 is not necessarily executed after the completionof the first state-keeping step S503, but is only required to beexecuted before the start of the ozone injection step S505 so as toprepare the ozone gas. The controller 61 first opens the fourthelectromagnetic valve 73 to supply the oxygen with a high concentrationto the ozone generators 32. The controller 61 may close the fifthelectromagnetic valve 74 and open the sixth electromagnetic valve 75 forseveral tens of seconds from the start of driving the ozone generators32, so as to lead the ozone gas to flow through the piping system of thefirst catalyst tank 42 without supplying the ozone gas to the buffertank 23 until the concentrations of the oxygen and the ozone are stable.The controller 61 then closes the sixth electromagnetic valve 75 andopens the fifth electromagnetic valve 74, so as to fill the buffer tank34 with the ozone gas until reaching a predetermined flowing amount, apredetermined concentration, and a predetermined period of time. Thecontroller 61 after finishing filling the buffer tank 34 with the ozonegas closes the fifth electromagnetic valve 74 to stop driving the ozonegenerators 32.

The ozone injection step S505 is a step of injecting the ozone gasproduced in the ozone preparation step S504 to the chamber 11. FIG. 3indicates the timing of starting the ozone injection step S505 by T13.The ozone injection step S505 is executed after the completion of thefirst state-keeping step S503. The controller 61 opens the seventhelectromagnetic valve 76 and further opens the second electromagneticvalve 71 and the third electromagnetic valve 72 for a predeterminedperiod of time such as five seconds to inject the ozone gas to thechamber 11. The pressure inside the buffer tank 34 is set to apredetermined pressure in a range of about 0.03 to 0.08 MPa to themaximum as a gauge pressure, or a predetermined pressure in a range ofabout 0.13 to 0.18 MPa as an absolute pressure. The injection of theozone gas to the inside of the chamber 11 under the decompression of3000 Pa or less as an absolute pressure is presumed to be completedwithin about several seconds due to the pressure difference.

The ozone supply unit 30 as described above injects the ozone gas to theinside of the chamber 11 in response to the increase in the pressure ofthe ozone gas in the buffer tank 34. The above-describe injection of theozone gas further facilitates the equalization of the diffusion of theozone gas inside the chamber 11. In addition, the ozone gas easilyenters the inside of a tube of the object to be sterilized having a ductpart.

The ozone injection step S505 injects the ozone gas to the inside of thechamber 11 through the inside of the evaporator 26, so as to use theozone gas to push the hydrogen peroxide remaining in the evaporator 26into the chamber 11 to further improve the sterilization effect. Thesterilizer 100 can share the introduction port provided in the chamber11 to be used as the port to which the hydrogen peroxide is introducedand the port to which the ozone gas is introduced, so as to simplify thecircumferential configuration of the chamber 11.

The sterilization step S500 further includes a second vapor preparationstep S506, a second vapor injection step S507, an outside air injectionstep S508, and a second state-keeping step S509.

The second vapor preparation step S506 is a step of producing the vaporof the second aqueous solution to be injected in the following secondvapor injection step S507. The second vapor preparation step S506 is notnecessarily executed after the completion of the ozone injection stepS505, but is only required to be executed before the start of the secondvapor injection step S507 so as to prepare the vapor of the secondaqueous solution. The generation of the vapor of the second aqueoussolution may be executed through a process similar to the generation ofthe vapor of the first aqueous solution in the first vapor preparationstep S501.

The controller 61 first rotates the second tube pump 23 b to suck thesecond aqueous solution from the second bottle 21 b, and then injects anequally-divided amount of the defined amount to the storage part 24. Forexample, when the treatment mode is the short mode, the concentration ofthe hydrogen peroxide contained in the second aqueous solution is set toa predetermined concentration (x2) in a range of 0.1% to 10%, and thedefined amount is a predetermined amount (y2) in a range of 2 to 8 ml.When the defined amount is divided by two and is then injected, forexample, the equally-divided amount of the defined amount is half of y2,which is a predetermined amount (y2/2) in a range of 1 to 4 ml. Thecontroller 61 then opens the first electromagnetic valve 70 for apredetermined period of time such as five seconds. Since the inside ofthe evaporator 26 has been already decompressed, the second aqueoussolution is immediately sucked up to the evaporator 26. The air thenenters the storage part 24, which communicates with the atmosphere, viathe first filter 25 so that the second aqueous solution remaining in thestorage part 24 or the first supply pipe 27 is also sent to theevaporator 26. The controller 61 then closes the first electromagneticvalve 70 to evaporate the second aqueous solution in the evaporator 26for a predetermined period of time such as five seconds. The evaporator26 is constantly kept at a predetermined temperature in a range of 65°C. to 120° C., for example. When a regulated amount of the secondaqueous solution is injected so as to be substantially completelyevaporated inside the evaporator 26 with a predetermined value within acapacity in a range of 0.5 to 2 L under a pressure of 50 Pa, forexample, the pressure is presumed to be increased to a level of about asaturated vapor pressure. The controller 61 then leads the process toproceed to the second vapor injection step S507 after the second vaporpreparation step S506.

The second vapor injection step S507 is a step of injecting the vapor ofthe second aqueous solution produced by the evaporator 26 to the insideof the chamber 11. FIG. 3 indicates the timing of starting the secondvapor injection step S507 by T14. The ozone itself cannot contribute tothe sterilization well, but increases the reactivity when moisture isadded thereto. The reason for this is presumed that a OH radical or thelike is produced when the ozone reacts with moisture or the remaininghydrogen peroxide on surfaces of bacteria so as to effectively destroycell walls of the bacteria. In view of this, the present embodimentinjects the vapor of the second aqueous solution to the inside of thechamber 11 immediately after the completion of the injection of theozone gas. The hydrogen peroxide contained in the vapor injected to theinside of the chamber 11 is presumed to penetrate cells of the bacteriathrough the cell walls destroyed by the ozone to attack cell nuclei, soas to improve the sterilization effect.

With regard to the relationship between the first aqueous solution andthe second aqueous solution, the concentration of the hydrogen peroxidecontained in the second aqueous solution may be lower than or equal tothe concentration of the hydrogen peroxide contained in the firstaqueous solution.

The injection of the vapor of the first aqueous solution is defined as amain sterilization treatment using the hydrogen peroxide as a materialfor the sterilization gas. The injection of the vapor of the secondaqueous solution is defined as an auxiliary treatment for improving thesterilization efficiency of the sterilization treatment due to theinjection of the ozone gas. When the vapor of the second aqueoussolution is injected in the second vapor injection step S507, theconcentration of the hydrogen peroxide contained in the aqueous solutioncan be set to be lower for the second aqueous solution than for thefirst aqueous solution, or set to be equal to each other. This candecrease the used amount of the hydrogen peroxide in the entiresterilization treatment when the sterilizing method according to thepresent embodiment uses both the first aqueous solution and the secondaqueous solution. In addition, the amount of the hydrogen peroxide thatmay remain on the surface of the object to be sterilized or inside thechamber 11 can be decreased in proportion to the decrease in the usedamount of the hydrogen peroxide.

Alternatively, with regard to the relationship between the first aqueoussolution and the second aqueous solution, the total amount of thehydrogen peroxide contained in the second aqueous solution may besmaller than or equal to the total amount of the hydrogen peroxidecontained in the first aqueous solution.

Setting the total amount of the hydrogen peroxide contained in thesecond aqueous solution to be smaller than or equal to the total amountof the hydrogen peroxide contained in the first aqueous solution candecrease the used amount of the hydrogen peroxide in the entiresterilization treatment regardless of whether the concentration of thehydrogen peroxide contained in the second aqueous solution is higherthan the concentration of the hydrogen peroxide contained in the firstaqueous solution.

The concentration of the hydrogen peroxide contained in the firstaqueous solution or the second aqueous solution, or the total amount ofthe hydrogen peroxide contained in the first aqueous solution or thesecond aqueous solution may be defined in accordance with the presenceor absence of a duct part in the object to be sterilized or the materialused for the object to be sterilized.

The present embodiment illustrates the three treatment modes that differfrom each other in the presence or absence of a duct part in the objectto be sterilized or the material used for the object to be sterilized.For example, the object to be sterilized to which the sterilizationtreatment in the normal mode can be subjected is a thin tube made ofresin. The object to be sterilized to which the sterilization treatmentin the long mode can be subjected is a thin tube made of stainlesssteel. With regard to the comparison between the thin tube of resin andthe thin tube of stainless steel, the thin tube of stainless steel istypically harder to sterilize than the thin tube of resin. The reasonfor this is presumed that the reactivity between a transition elementsuch as Fe, Mo, or Cr contained in stainless steel and the hydrogenperoxide is high, and the hydrogen peroxide is thus decomposed in themiddle of the treatment to impede the sufficient supply of the hydrogenperoxide to the inside of the thin tube. Another reason for this ispresumed that the thin tube of stainless steel has higher thermalconductivity than the thin tube of resin, and is cooled under adecompressed environment more quickly to easily cause water condensationof the hydrogen peroxide inside the thin tube, which impedes thesufficient supply of the hydrogen peroxide to the inside of the thintube.

When the thin tube of stainless steel is sterilized, for example, thepresent embodiment can deal with the above-described problem such thatthe concentration of the hydrogen peroxide contained in the secondaqueous solution is set to be higher than the concentration of thehydrogen peroxide contained in the second aqueous solution used in theother treatment modes. The concentration of the hydrogen peroxidecontained in the second aqueous solution in this case still does notexceed the concentration of the hydrogen peroxide contained in the firstaqueous solution. When the concentration of the hydrogen peroxidecontained in the second aqueous solution is equal to the concentrationof the hydrogen peroxide contained in the first aqueous solution, theinjected amount of the second aqueous solution can be decreased. Inother words, the present embodiment, when sterilizing the thin tube ofstainless steel, can particularly decrease the entire used amount of thehydrogen peroxide (the concentration of the hydrogen peroxide in thefirst aqueous solution and the second aqueous solution×the sum of theinjected amount of the hydrogen peroxide), as compared with conventionalsterilizing methods. The same is also applied to the case in which thetotal amount of the hydrogen peroxide contained in the second aqueoussolution is smaller than or equal to the total amount of the hydrogenperoxide contained in the first aqueous solution, so as to accuratelydecrease the entire used amount of the hydrogen peroxide (the sum of thetotal amount of the hydrogen peroxide in the first aqueous solution andthe total amount of the hydrogen peroxide in the second aqueoussolution).

The sterilization effect is increased as the concentration of thehydrogen peroxide contained in the second aqueous solution is higher.The increase in the concentration of the hydrogen peroxide contained inthe second aqueous solution can be presumed to lead to a reduction inthe treatment time. The present embodiment is illustrated with a case,when the treatment mode is the long mode, in which the concentration ofthe hydrogen peroxide contained in the second aqueous solution is set tothe predetermined concentration (x1) in the range of 30% to 60% that isequal to the concentration of the hydrogen peroxide contained in thefirst aqueous solution. While the injected amount per pulse in the shortmode or the normal mode is set to the predetermined value (y2) in therange of 2 to 8 ml, the injected amount in the long mode can be set to asmaller predetermined amount (y3) in a range of 1 to 5 ml.

As described above, the second vapor injection step S507 is executedimmediately after the completion of the ozone injection step S505. Theinjection of the vapor of the second aqueous solution may be executedthrough a process similar to the injection of the vapor of the firstaqueous solution in the first vapor injection step S502.

The controller 61 first opens the second electromagnetic valve 71 andthe third electromagnetic valve 72 for a predetermined period of timesuch as ten seconds, and injects the vapor of the second aqueoussolution to the chamber 11. The controller 61 then closes the secondelectromagnetic valve 71 and the third electromagnetic valve 72. Thecontroller 61 repeats the injection of the vapor of the second aqueoussolution in the same process in accordance with the respective treatmentmodes. When the treatment mode is the short mode, the controller 61 inthis case may also divide the amount of the second aqueous solution ofy2 (2 to 8 ml) by two so as to evaporate and sequentially inject thesecond aqueous solution half-and-half to the chamber 11, for example.The controller 61 may divide the amount of the second aqueous solutioninto more than two so as to sequentially inject the vapor of the secondaqueous solution to the chamber 11. The controller 61 then leads theprocess to proceed to the outside air injection step S508 after thesecond vapor injection step S507.

While the present embodiment is illustrated above with the case ofinjecting the vapor of the second aqueous solution of the hydrogenperoxide in the second vapor injection step S507, the method may injectvapor produced from water or a solution containing a volatile compounddescribed below, instead of the second aqueous solution. The water usedfor producing the vapor may be water in which pyrogen is removed orinactivated, or water in which bacteria or microbes are removed orinactivated. The use of the water in which pyrogen is removed orinactivated or the water in which bacteria or microbes are removed orinactivated can preliminarily prevent contamination of the object to besterilized caused by pyrogen and the like. The water as used herein maybe pure water or ultrapure water such as purified water to whichsterilization or disinfection treatment is subjected. The volatilecompound may be sodium hypochlorite or alcohols. An example of alcoholsmay be ethanol.

The following is an example of injecting the vapor of the pure water inthe second vapor injection step S507, instead of the second aqueoussolution, in which the pure water is stored in the second bottle 21 b.The pure water is evaporated by the evaporator 26. The use of the purewater instead of the second aqueous solution can also have the advantageof improving the reactivity of the ozone gas, as in the case describedabove. The table shown in FIG. 4 illustrates the case in which theconcentration of the hydrogen peroxide contained in the second aqueoussolution in the short mode and the normal mode (x2: a predeterminedvalue in a range of 0.1% to 10%) is greatly lower than the concentrationof the hydrogen peroxide contained in the first aqueous solution (x1: apredetermined value in a range of 30% to 60%). In the case in which oneof these two treatment modes can be chosen and the sterilization effectis not strictly required for the object to be sterilized, for example,the pure water can be used instead of the second aqueous solution. Thiscan decrease the used amount of the hydrogen peroxide in the entiresterilization treatment.

In the outside air injection step S508 is a step of injecting theoutside air that is the atmosphere or dry nitrogen gas to the inside ofthe chamber 11. FIG. 3 indicates the timing of starting the outside airinjection step S508 by T15. The present embodiment is illustrated belowwith a case in which the outside air is the atmosphere. The outside airinjection step S508 is executed immediately after the completion of thesecond vapor injection step S507. The injection of the air to the insideof the chamber 11 pushes the hydrogen peroxide or the ozone gascongested particularly in the middle of the duct part in the object tobe sterilized, so as to further promote the sterilization. The injectionof the air to the inside of the chamber 11 also equalizes thedistribution of the concentration of the gas present inside the chamber11 so as to ensure the uniform sterilization. The injection of the airto the inside of the chamber 11 further increases the internal pressureto lead the hydrogen peroxide in the vapor to be slightly condensed onthe surface of the object to be sterilized, so as to improve thesterilization effect. The condensation as used herein is referred toalso as micro-condensation. Particularly when the outside air is theatmosphere, the cost for the raw material for the gas to be injected canbe eliminated, and the configuration for injecting the air to the insideof the chamber 11 can be simplified, so as to reduce the manufacturingcosts for the sterilizer 100.

The controller 61 injects the air into the inside of the chamber 11 viathe air introduction unit 50. In particular, the controller 61 controlsthe open and closed states of the ninth electromagnetic valve 78 and thetenth electromagnetic valve 79 as appropriate, so as to regulate theinjected amount of the air introduced through the second filter 51. Theair is continuously introduced until reaching a predetermined pressure.In the present embodiment, the controller 61 closes the ninthelectromagnetic valve 78 and the tenth electromagnetic valve 79 afterinjecting the air until the pressure inside the chamber 11 reaches about90 kPa that is about 90% of the atmospheric pressure. The reason forthis is that the gas may leak out of the door 12 through the sealingpart if the internal pressure of the chamber 11 is equal to the externalpressure. The controller 61 then leads the process to proceed to thesecond state-keeping step S509 after the outside air injection stepS508.

As described above, the outside air injection step S508 is effectiveparticularly upon choosing the normal mode or the long mode that isapplied to the case in which the object to be sterilized has a ductpart. In the case of the short mode for mainly executing the surfacesterilization on the object to be sterilized not having a duct part, theoutside air injection step S508 is not necessarily executed in view ofthe simplification of the step when the short mode can ensure thepreferable sterilization effect.

The second state-keeping step S509 is a step of keeping the state of theinside of the chamber 11 for a predetermined period of time after thecompletion of the outside air injection step S508. FIG. 3 indicates thepredetermined keeping time by H15. Keeping the state of the inside ofthe chamber 11 for the predetermined period of time can further promotethe sterilization action as described in the outside air injection stepS508. The keeping time in the respective treatment modes as used hereindiffers from each other. The keeping time in the short mode is twominutes, for example. The keeping time in the normal mode is threeminutes, for example. The keeping time in the long mode is five minutes,for example.

The sterilization step S500 as described above may be repeated severaltimes as necessary depending on the object to be sterilized. Thecontroller 61 then determines whether the operation of the sterilizationstep S500 needs to be repeated (step S600) as shown in FIG. 2 after thecompletion of the second state-keeping step S509. The first operation ofthe sterilization step S500 is counted as one as the number of theexposure times, and the number of the exposure times in the followingsteps is indicated by the pulse number. The controller 61, whendetermining that the sterilization step S500 needs to be repeated (YES),leads the process to proceed to the sterilization decompression stepS400 to decompress so as to execute the sterilization step for thesecond pulse. When determining that no more sterilization step is needed(NO), the controller 61 leads the process to proceed to the followingthe aeration step S700.

The number of pulses required is defined so as to ensure a sterilizationsecurity standard of 10⁻⁶ or lower (SAL<10⁻⁶). To achieve the standard,the sterilization step in a half cycle corresponding to one pulse needsto annihilate 10⁻⁶ or greater of indicator bacteria. The presentembodiment defines two pulses as a full cycle in all of the threetreatment modes.

The aeration step S700 is a step of decompressing the inside of thechamber 11 to a predetermined vacuum degree to remove the hydrogenperoxide and the ozone as the sterilization gas, and then injecting theair to reach a level of about the atmospheric pressure so as to dilutethe sterilization gas. In the present embodiment, the treatmentoperation in the aeration step S700 in the short mode differs from theother treatment modes.

First, the aeration step S700 in the case of the treatment mode that isthe short mode is described below. The time for the contact between thesterilization gas and the object to be sterilized is shorter for theshort mode than for the other modes. The aeration step S700 in this caseincludes the following treatment step, for example, so as to decreasethe treatment time.

The controller 61 first starts operating the vacuum pump 41 and opensthe eighth electromagnetic valve 77 to start the decompression of theinside of the chamber 11 immediately after the completion of the secondstate-keeping step S509 as early as possible. Simultaneously, thecontroller 61 opens the second electromagnetic valve 71, the thirdelectromagnetic valve 72, and the seventh electromagnetic valve 76, soas to discharge the remaining gas inside the evaporator 26 and thebuffer tank 34. The short mode keeps decompressing the inside of thechamber 11 until the internal pressure reaches 100 Pa, for example. Thesterilization gas discharged passes through the first catalyst tank 42and the second catalyst tank 43, so as to lead the hydrogen peroxide tobe decomposed to be harmless water and oxygen and lead the ozone to bedecomposed to be harmless oxygen to be discharged to the outside of thesterilizer 100 with a concentration of a safety management value orlower. The controller 61 then closes the eighth electromagnetic valve 77when the pressure inside the chamber 11 reaches a predetermineddecompressed pressure.

The controller 61 then opens the ninth electromagnetic valve 78 and thetenth electromagnetic valve 79 to inject the air to the inside of thechamber 11 through the second filter 51. Simultaneously, the controller61 opens the second electromagnetic valve 71, the third electromagneticvalve 72, and the seventh electromagnetic valve 76 to inject the airalso to the inside of each of the evaporator 26 and the buffer tank 34.The injected air diffuses and dilutes the gas remaining inside thechamber 11, and removes the sterilization gas adhering to the object tobe sterilized or the inner surface of the chamber 11. The controller 61keeps injecting the air until the pressure inside the chamber 11 reachesabout 90 kPa that is about 90% of the atmospheric pressure, and thencloses the ninth electromagnetic valve 78 and the tenth electromagneticvalve 79.

The controller 61 repeats the decompression and the air injection asdescribed above for the prescribed number of times. In the short mode,the total repeated number of times may be three. When the time requiredfor the decompression is presumed to be about three minutes and the timerequired for the air injection is presumed to be about 0.5 minutes, theaeration step S700 is to take the time given by 3.5 minutes×threetimes=10.5 minutes. The controller 61 returns the pressure inside thechamber 11 to the atmospheric pressure by the air injection afterrepeating the decompression and the air injection for the prescribednumber of times, and finishes the aeration step S700. The controller 61ends the sterilization treatment after the aeration step S700.

Second, the aeration step S700 in the case of the treatment mode that isthe other modes other than the short mode is described below. The timefor the contact between the sterilization gas and the object to besterilized, and the amount of the hydrogen peroxide adhering to theobject to be sterilized or the amount of the hydrogen peroxide remaininginside the chamber 11 are greater for the other modes than the shortmode. The aeration step S700 in this case includes the followingtreatment step, for example.

The fundamental operations of the decompression and the air injectionare the same as those in the case in which the treatment mode is theshort mode. The pressure reaching upon the decompression, which is setto 100 Pa or lower in the short mode, is set to 50 Pa or lower in theother modes, for example, which is stricter than the case of the shortmode, since the object to be sterilized can have a duct part in theother modes.

The controller 61 keeps executing the decompression while injecting theair after the completion of the first decompression and air injection.In particular, the controller 61 starts operating the vacuum pump 41 andopens the eighth electromagnetic valve 77 to start the decompression,and then opens the ninth electromagnetic valve 78 and the tenthelectromagnetic valve 79 after a delay of about two seconds, forexample, so as to inject the air through the second filter 51. A timingof stopping the air injection at the time of injecting the air after thedecompression is presumed to be a point at which the pressure inside thechamber 11 is led to about 90 kPa or greater. A timing of stopping theair injection at the time of decompressing while injecting the air maybe set to a point at which the pressure inside the chamber 11 is led toabout 90 kPa or lower. The exhaustion during the air injection activatesthe flow of the air, so as to actively remove the sterilization gasadhering to the object to be sterilized or the inner surface of thechamber 11. In particular, since the object to be sterilized is wrappedwith the wrapping material upon the normal sterilization treatment, thesterilization gas adsorbed to the wrapping material can be effectivelyremoved. The time for decompressing while injecting the air is set toabout five minutes, for example. The time required for each treatmentfor the exhaustion during the air injection is shorter than the timerequired for each treatment for the air injection after thedecompression, so as to reduce the entire time necessary for theaeration step S700 accordingly.

The controller 61 further repeats the operations similar to thedecompression and the air injection executed first. The repeating timein this case may be two, for example.

The aeration step S700 in this case takes about 15.5 minutes in total,in which the time required for the first decompression and air injectionis 3.5 minutes, the time required for decompressing while injecting theair is 5 minutes, and the time required for the second decompression andair injection is 3.5 minutes×2=7 minutes. The controller 61 then returnsthe pressure inside the chamber 11 to the atmospheric pressure by theair injection, and finishes the aeration step S700. The controller 61ends the sterilization treatment after the aeration step S700.

While the aeration step S700 repeats the decompression and the airinjection several times as described above, which is effective toeliminate the remaining sterilization gas, the treatment time isincreased as the repeating number is increased. When the decompressionand the air injection are repeated five times, for example, the time(five minutes) shorter than the time (six minutes) taken for repeatingtwo times (three minutes×two times) may be substituted for the nextrepeating time. This can discharge the sterilization gas remaininginside the chamber 11 more effectively, and further reduce the timerequired for the aeration step S700.

The treatment time taken for the sterilization treatment according tothe present embodiment described above in each treatment mode issubstantially as indicated in the table shown in FIG. 3 . The operatorremoves the object to be sterilized from the chamber 11 after thecompletion of the series of the steps for the sterilization treatment.

The effects achieved by the sterilizing method and the sterilizer 100that can execute the sterilizing method according to the presentembodiment are described below.

The sterilizing method according to the present embodiment is tosterilize the object to be sterilized housed in the chamber 11, andincludes the first vapor injection step S502 of injecting, to the insideof the chamber 11, the vapor generated from the first aqueous solutionof the hydrogen peroxide. The sterilizing method also includes the ozoneinjection step S505 of injecting the ozone gas to the inside of thechamber 11 after the first vapor injection step S502. The sterilizingmethod further includes the second vapor injection step S507 ofinjecting, to the inside of the chamber 11, the vapor generated from thesecond aqueous solution of the hydrogen peroxide. The total amount ofthe hydrogen peroxide contained in the second aqueous solution issmaller than or equal to the total amount of the hydrogen peroxidecontained in the first aqueous solution.

The sterilizer 100 according to the present embodiment includes thechamber 11 that houses the object to be sterilized, and the evaporator26 that communicates with the chamber 11, and evaporates the firstaqueous solution of the hydrogen peroxide or the second aqueous solutionof the hydrogen peroxide so as to be filled therewith. The sterilizer100 also includes the ozone generators 32 that communicates with thechamber 11, and produces the ozone gas. The sterilizer 100 furtherincludes the controller 61 that controls the operation of injecting, tothe inside of the chamber 11, the vapor produced by the evaporator 26 orthe ozone gas produced by the ozone generators 32. The total amount ofthe hydrogen peroxide contained in the second aqueous solution issmaller than or equal to the total amount of the hydrogen peroxidecontained in the first aqueous solution. The controller 61 injects theozone gas to the inside of the chamber 11 after injecting the vaporproduced from the first aqueous solution, and injects the vapor producedfrom the second aqueous solution after injecting the ozone gas, so as tosterilize the object to be sterilized.

The sterilizing method and the sterilizer 100 as described above subjectthe object to be sterilized to the sterilization treatment using thevapor of the first aqueous solution and then to the sterilizationtreatment using the ozone gas. The present embodiment further injectsthe vapor of the second aqueous solution after injecting the ozone gasto the inside of the chamber 11. This can improve the reactivity of theozone gas, so as to increase the sterilization efficiency of thesterilization treatment more than a case of executing the sterilizationtreatment only using the ozone gas.

The injection of the vapor of the first aqueous solution is defined as amain sterilization treatment using the hydrogen peroxide as a materialfor the sterilization gas. The injection of the vapor of the secondaqueous solution is defined as an auxiliary treatment for improving thesterilization efficiency of the sterilization treatment due to theinjection of the ozone gas. When the vapor of the second aqueoussolution is injected in the second vapor injection step S507, the totalamount of the hydrogen peroxide contained in the aqueous solution can beset to be smaller for the second aqueous solution than for the firstaqueous solution, or set to be equal to each other. This can decreasethe used amount of the hydrogen peroxide in the entire sterilizationtreatment. In addition, the amount of the hydrogen peroxide that mayremain on the surface of the object to be sterilized or inside thechamber 11 can be decreased in proportion to the decrease in the usedamount of the hydrogen peroxide.

The sterilizing method and the sterilizer 100 according to the presentembodiment thus can improve the sterilization efficiency and alsodecrease the used amount of the hydrogen peroxide in the entiresterilization treatment.

Second Embodiment

FIG. 6 is a flowchart showing a process of a sterilizing methodaccording to a second embodiment. The sterilizing method according tothe first embodiment includes the ozone adsorption step S300 for causingthe ozone gas to be preliminarily adsorbed to the wrapping materialwrapping the object to be sterilized. When the adsorption amount of theozone gas to be adsorbed to the wrapping material when the ozone gas isinjected to the inside of the chamber 11 in the ozone injection stepS505 can be presumed not to have a great influence on the sterilizationefficiency, the ozone adsorption step S300 and further the preliminarydecompression step S200 and the sterilization decompression step S400 inrelation to the ozone adsorption step S300 executed in the firstembodiment may be eliminated in the second embodiment.

As described above, the sterilizing method according to the presentembodiment does not employ the preliminary decompression step S200, theozone adsorption step S300, or the sterilization decompression stepS400, as shown in FIG. 6 . Instead, the sterilizing method according tothe present embodiment additionally includes a first decompression stepS110 before the first vapor injection step S502 in the sterilizationstep S500 since the inside of the chamber 11 still needs to bedecompressed. The target pressure set in the first decompression stepS110 and the control executed by the controller 61 until reaching thetarget pressure may be the same as those described in the sterilizationdecompression step S400.

The sterilizing method and the sterilizer 100 according to the presentembodiment are described below in reference to Example in comparisonwith two comparative examples.

FIG. 7 is a table showing various kinds of conditions for sterilizationtreatment tests executed for Comparative Example 1 and ComparativeExample 2, in addition to Example according to the present embodiment.FIG. 8 is a table showing results of each test executed under theconditions shown in FIG. 7 . FIG. 8 shows a negative rate for each test.The column on the left side of the negative rate indicates the number ofbiological indicators used as described below that show the negativerate. The respective tests were executed for three days, and therespective values in parentheses in the column of the negative rateindicate the test results obtained in each day.

The respective tests use strip-type biological indicators (BIs) suitablefor mainly evaluating the surface sterilization for the object to besterilized for ease of comparison of the sterilization effect. Inparticular, the BI used in each test is HMV-091-type available from APEX(bacterium number: ATCC12980, 21×10⁶ cfu/disc, D value: 1.0 min). Theterm “D value” refers to a time necessary for annihilating 90% of testbacteria and decreasing a survival rate to one tenth. Three to five BIsare exposed per test. Since the BIs used are not a thin tube having aduct part, the step of the air injection corresponding to the outsideair injection step S508 in the present embodiment is omitted so as tofacilitate the comparison particularly between Example and ComparativeExample 1.

A chamber used in each test is presumed to have the same structure underthe same conditions as the chamber 11 described above. In particular,the capacity of the chamber 11 is 100 L, and is preliminarily heated to50° C. Only the BIs are preliminarily housed in the chamber 11. Theother test conditions are as shown in FIG. 8 . The injected amount ofthe aqueous solution of the hydrogen peroxide injected in the first time(referred to below as a “first aqueous solution” in all the tests forillustration purposes) is set to be the same in all the tests for easeof comparison.

FIG. 9 is a graph showing a change in pressure inside the chamber 11 inComparative Example 1. The sterilization step in Comparative Example 1simulates the sterilizing method disclosed in Patent Literature 1. InComparative Example 1, the vapor of the first aqueous solution isinjected to the inside of the chamber 11 at a timing T21 after thedecompression, and is kept during a period H21. The ozone gas is theninjected to the inside of the chamber 11 at a timing T22, and is keptduring a period H22. The aeration step is finally executed at a timingT23.

FIG. 10 is a graph showing a change in pressure inside the chamber 11 inComparative Example 2. The sterilization step in Comparative Example 2does not execute the injection of the ozone gas. In Comparative Example2, the vapor of the first aqueous solution is injected to the inside ofthe chamber 11 at a timing T31 after the decompression, and is keptduring a period H31. The air is then injected to the inside of thechamber 11 at a timing T32. The aeration step is finally executed.

FIG. 11 is a graph showing a change in pressure inside the chamber 11 inExample. In Example, the vapor of the first aqueous solution is injectedto the inside of the chamber 11 at a timing T1 after the decompression(the first vapor injection step S502), and is kept during a period H1(the first state-keeping step S503). The ozone gas is then injected tothe inside of the chamber 11 at a timing T2 (the ozone injection stepS505). The vapor is continuously injected to the inside of the chamberat a timing T3 and a timing T4 (the second vapor injection step S507),and is kept during a period H2 (the second state-keeping step S509).While the sterilization step is illustrated above with the case ofinjecting the vapor of the second aqueous solution in the second vaporinjection step S507, Example uses the vapor of pure water as an exampleof not having the sterilization effect when assumed to be usedindependently. The aeration step is finally executed at a timing T5.

The results of the respective tests revealed that, as shown in FIG. 8 ,upon the comparison of the negative rate in each test, Example has thehigher negative rate than Comparative Example 1 or Comparative Example2, showing that Example has the higher sterilization effect thanComparative Example 1 or Comparative Example 2.

The sterilizing method as described above can reduce the timecorresponding to the ozone adsorption step S300, when omitted, and stillavoid a decrease in the sterilization effect regardless of the omissionof the ozone adsorption step S300, so as to further decrease theoperating time of the sterilizer 100 for executing the sterilizingmethod.

It should be understood that the present disclosure includes variousembodiments not described herein.

REFERENCE SIGNS LIST

-   -   11 CHAMBER    -   26 EVAPORATOR    -   32 OZONE GENERATOR    -   61 CONTROLLER    -   100 STERILIZER

The invention claimed is:
 1. A sterilizing method for sterilizing asterilization object housed in a chamber, the method comprising: a firstvapor injection step of injecting vapor produced from a first aqueoussolution of hydrogen peroxide to an inside of the chamber; an ozoneinjection step of injecting ozone gas to the inside of the chamber afterthe first vapor injection step thereby mixing the vapor from the firstvapor injection step with the ozone; and a second vapor injection stepof injecting vapor produced from a second aqueous solution of hydrogenperoxide to the inside of the chamber after the ozone injection stepthereby mixing the vapor from the first vapor injection step and thesecond vapor injection step with the ozone, wherein a total amount ofthe hydrogen peroxide included in the second aqueous solution is smallerthan or equal to a total amount of the hydrogen peroxide included in thefirst aqueous solution, wherein a concentration of the hydrogen peroxideincluded in the second aqueous solution is higher than a concentrationof the hydrogen peroxide included in the first aqueous solution.